In recent years there has been proposed a steering control device for vehicles equipped with a so-called steer-by-wire system (hereinafter referred to as “SBW system”), in which a mechanical connection between a steering member, such as a steering wheel, and the steered wheel is disconnected and a part of the steering system is structured with an electric route. In this type of SBW system, for example, there have been proposals for structures such that when an abnormality is detected in the reaction force actuator, the control of the reaction force is cancelled and a mechanical backup system is activated that mechanically connects the steering member and steered wheels, and steering control is switched to control with steering assistance, thereby controlling the steering wheel actuator and functioning as a normal electric power steering (EPS) device. For example, see Laid-open Japanese Patent Application No. 2004-090783.
However, conventional devices do not recognize reduction of the power supply capacity of the vehicle as an abnormality in the SBW control system.
The present steering control device is focused on the above-description, and provides low power consumption while maintaining desirable responsive steering performance during a period of reduced power supply capacity.
More particularly, the present steering control device, in which a steering portion having an electric steering reaction force actuator and a steered portion having an electric steered portion actuator are mechanically disconnectable and connectable via backup means, includes steer-by-wire control means for disconnecting the backup means and carrying out steer-by-wire control using control of the steered portion actuator in establishing a steered angle corresponding to the steering condition and a control for the steering reaction force actuator that adds a steering reaction force that corresponds to the steered condition. Control switching means is provided for switching between steer-by-wire control and a conventional steering system. Power supply capacity estimating means is provided for estimating the power supply capacity of the vehicle. The control switching means selectively switches to conventional steering control when the power supply capacity is reduced to a predetermined value or lower during steer-by-wire control.
Therefore, in accordance with the present steering control device, when the estimated power supply capacity is reduced to a predetermined value or lower during steer-by-wire control, the control switch means switches to conventional steering control.